In the prior art different devices and methods for sterilizing packaging materials are known. One method widely used in the prior art is sterilization by means of gases and in particular by means of hydrogen peroxide. However, efforts are being made to reduce the use of chemicals when sterilizing containers. Therefore, devices and methods have also become known which sterilize material by means of ultraviolet radiation or electron beams. In general for electron beams, there is provided an emitter that is adapted to emit charge carriers, in particular electrons, wherein the packaging material can be sterilized by these charge carriers. For this purpose the packaging material and the emitter, respectively, are moved relative to each other, e.g. an electron gun is put into a bottle-shaped package. However, when the emitter and the packaging material are moved relative to each other, flows or streams of a medium, such as air, are established in between. If these streams or flows comprise a medium, such as air, that is not sterile or aseptic, there exists the risk that parts of the packaging material that have already been sterilized are re-infected by the unsterile or non-aseptic air-streams or—flows.